3. Definition
• Apoptosis is a pathway of cell death in which cells
activate enzymes that degrade the cells own nuclear
DNA and nuclear & cytoplasmic proteins.
• Greek word – “falling off” or “dropping off”
4. Cause
1. Physiological:
• Eliminate cells that are no longer needed and to maintain a
constant number of cells of various types in tissue.
2. Pathological:
• Apoptosis eliminates cells that are genetically altered or
injured beyond repair
5. Physiological cause
1. During embryogenesis
2. Involution of hormone-dependent tissues
3. Involution of the thymus in early age
4. Normal cell destruction followed by replacement
Proliferation such as in intestinal epithelium.
6. Pathological cause
1. Cell death in tumours – in chemotherapy
2. Cell death by cytotoxic t cells
3. Cell death in viral infections
4. Pathologic atrophy
5. Degenerative diseases of CNS
6. Heart diseases
7. Morphology
• Pyknosis – Condensed chromatin
• Karyorrehexis – Fragmented nuclear chromatin
• No acute inflammatory reaction
• Apoptotic bodies - Formation of membrane-bound near
spherical bodies on or around the cell
8.
9. Mechanism
• Caspases – activation of the enzyme
• Mitochondrial pathway ( intrinsic)
• Death receptor pathway ( Extrinsic)
• Pro apoptotic
• Anti apoptotic
• Sensors - BAD,BIM,BID,PUMA,NOXA
